Implement <sys/fsuid.h>.

Change-Id: I1e5e50444a1b5a430ba5b5d9b8b1d91219af5e92
diff --git a/libc/arch-arm64/syscalls/setfsgid.S b/libc/arch-arm64/syscalls/setfsgid.S
new file mode 100644
index 0000000..d2f29ab
--- /dev/null
+++ b/libc/arch-arm64/syscalls/setfsgid.S
@@ -0,0 +1,14 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(setfsgid)
+    mov     x8, __NR_setfsgid
+    svc     #0
+
+    cmn     x0, #(MAX_ERRNO + 1)
+    cneg    x0, x0, hi
+    b.hi    __set_errno
+
+    ret
+END(setfsgid)